I found this recipe while searching for another recipe on the Internet. It's a very easy way to make Dulce de Leche. Works great as a filling for a chocolate or white cake.
Preheat the oven to 425° F .
Pour one can (400 gr/14 ounces) of sweetened condensed milk (not evaporated milk) into a glass pie plate or shallow baking dish.
Set the pie plate in a roasting pan, and add hot water until it reaches half way up the side of the pie plate.
Cover the pie plate tightly with aluminum foil and bake for 1 to 1¼ hours. (Check it a few times during baking and add more water to the roasting pan as necessary. I found that my oven takes more like 1-1/2 to 1-3/4 hours. I also like mine to be stiff enough that I can pipe it on cupcakes.)
Once the milk is browned and caramelized, remove from the oven and let cool. When it is cool, whisk it until smooth.
Store in the refrigerator until ready to use. If you need it warm, put it in the microwave for a few seconds or set in a pan of warm water.